#include<stdio.h>
long long f(long long x, int y)
{
	int n;   long long result = 1;
	for (n = 1; n <= y; n++)
	{result = result * n;}
	return result;
}
 int main()
 {
	long long a,b,i; int d;
	i = 0; d = 1; a = 0;
	while (d <= 20)
	{
		b = f(a,d);
		i = i + b; 
		d++;
	}
	printf("%lld", i);
	return 0;
 }
